From 4170b46544231e7cf1d64ac3baa314083be37502 Mon Sep 17 00:00:00 2001
From: Hennadii Stepanov <32963518+hebasto@users.noreply.github.com>
Date: Sat, 12 Sep 2020 18:05:54 +0300
Subject: [PATCH] p2p: Integrate DumpAnchors() and ReadAnchors() into CConnman

---
 src/net.cpp | 24 ++++++++++++++++++++++++
 src/net.h   |  6 ++++++
 2 files changed, 30 insertions(+)

diff --git a/src/net.cpp b/src/net.cpp
index 53cf4ca01..0fb4bf9bd 100644
--- a/src/net.cpp
+++ b/src/net.cpp
@@ -46,6 +46,12 @@ static_assert(MINIUPNPC_API_VERSION >= 10, "miniUPnPc API version >= 10 assumed"
 
 #include <math.h>
 
+/** Maximum number of block-relay-only anchor connections */
+static constexpr size_t MAX_BLOCK_RELAY_ONLY_ANCHORS = 2;
+static_assert (MAX_BLOCK_RELAY_ONLY_ANCHORS <= static_cast<size_t>(MAX_BLOCK_RELAY_ONLY_CONNECTIONS), "MAX_BLOCK_RELAY_ONLY_ANCHORS must not exceed MAX_BLOCK_RELAY_ONLY_CONNECTIONS.");
+/** Anchor IP address database file name */
+const char* const ANCHORS_DATABASE_FILENAME = "anchors.dat";
+
 // How often to dump addresses to peers.dat
 static constexpr std::chrono::minutes DUMP_PEERS_INTERVAL{15};
 
@@ -2431,6 +2437,15 @@ bool CConnman::Start(CScheduler& scheduler, const Options& connOptions)
         }
     }
 
+    if (m_use_addrman_outgoing) {
+        // Load addresses from anchors.dat
+        m_anchors = ReadAnchors(GetDataDir() / ANCHORS_DATABASE_FILENAME);
+        if (m_anchors.size() > MAX_BLOCK_RELAY_ONLY_ANCHORS) {
+            m_anchors.resize(MAX_BLOCK_RELAY_ONLY_ANCHORS);
+        }
+        LogPrintf("%i block-relay-only anchors will be tried for connections.\n", m_anchors.size());
+    }
+
     uiInterface.InitMessage(_("Starting network threads...").translated);
 
     fAddressesInitialized = true;
@@ -2546,6 +2561,15 @@ void CConnman::StopNodes()
     if (fAddressesInitialized) {
         DumpAddresses();
         fAddressesInitialized = false;
+
+        if (m_use_addrman_outgoing) {
+            // Anchor connections are only dumped during clean shutdown.
+            std::vector<CAddress> anchors_to_dump = GetCurrentBlockRelayOnlyConns();
+            if (anchors_to_dump.size() > MAX_BLOCK_RELAY_ONLY_ANCHORS) {
+                anchors_to_dump.resize(MAX_BLOCK_RELAY_ONLY_ANCHORS);
+            }
+            DumpAnchors(GetDataDir() / ANCHORS_DATABASE_FILENAME, anchors_to_dump);
+        }
     }
 
     // Close sockets
diff --git a/src/net.h b/src/net.h
index adeee1579..7b7885f83 100644
--- a/src/net.h
+++ b/src/net.h
@@ -566,6 +566,12 @@ private:
     /** Pointer to this node's banman. May be nullptr - check existence before dereferencing. */
     BanMan* m_banman;
 
+    /**
+     * Addresses that were saved during the previous clean shutdown. We'll
+     * attempt to make block-relay-only connections to them.
+     */
+    std::vector<CAddress> m_anchors;
+
     /** SipHasher seeds for deterministic randomness */
     const uint64_t nSeed0, nSeed1;